DE10236033A1 - Furnace, e.g. melting furnace for heating and containing materials subject to chemical reactions, includes container containing heat source and comprising refractory lining having first refractory lining layer, and optical waveguide - Google Patents

Abstract

Furnace comprises a container containing a heat source and comprising a refractory lining having a first refractory lining layer and container wall having intermediate layer(s) and an outer wall with an outer surface distal from the heat source, and at least one optical waveguide to monitor a temperature profile by optical back scattering measurement and located between the first lining layer and outer surface of the outer wall. A furnace comprises a heat source (80), a container containing the heat source and comprising a refractory lining (30) having a first refractory lining layer (A0) adjacent to the heat source and container wall (40) having intermediate layer(s) (W2, W3) and an outer wall (W1) with an outer surface (41) distal from the heat source, and at least one optical waveguide for monitoring a temperature profile by optical back scattering measurement. The waveguide is located between the first refractory lining layer and outer surface of the outer wall. The heat source provides the temperature profile in the refractory lining and in the container wall. Independent claims are also included for: (a) a method of thermally monitoring the condition of vital parts of the furnace, comprising coupling the optical waveguide to an optical back scattering measurement equipment, measuring a temperature distribution along the optical waveguide by an optical back scattering measurement, determining the temperature profile for the vital parts based on the measured temperature distribution, and assessing the condition of the vital parts based on the temperature profile; (b) a system of thermally monitoring the condition of the vital parts of the furnace, comprising the inventive furnace, an optical back scattering measurement equipment coupled to the optical waveguide, and a display for displaying the condition of the vital parts; (c) a method of monitoring the state of preservation of a refractory lining of melting furnaces, comprising arranging optical fibers between the wall and lining of the furnace to detect temperatures by a fiber-optic back scattering measuring system; and (d) a system for monitoring the condition of a refractory lining of melting furnaces comprising the temperature sensor.

Description

The invention relates to a method and an arrangement for monitoring the state of preservation of the refractory lining of melting furnaces.

In metal melting furnaces, especially in induction melting ovens subject the ceramic linings (oven lining) in operation very harsh thermal, chemical and mechanical loads. These lead to abrasion of the lining, i. to decrease their wall thickness, so that after fixed time intervals (6 to 8 weeks) the consumed Reinforced lining and a new lining be introduced got to.

Measuring methods for the condition or the state of wear of the lining are known. In a first temperature measuring system, a magnetic contact thermometer is mounted on the outer shell. Another temperature measurement method is based on pyrometry. Another measurement method is in the EP 519,231 B1 described. The principle consists of determining the conductivity of the refractory lining. For this purpose, an electrode network is incorporated in the lining, with which the associated with the abrasion change in the conductivity of the ceramic is measurable. The network provides a planar conductivity image in the lining, which is used to deduce the temperature conditions.

An electrical system has the disadvantage the electromagnetic susceptibility. The conductivity measuring system is strongly material dependent, which makes complex adjustment of the system necessary. The pyrometry has the disadvantage of punctual temperature determination only from the outside, and is only for determining the surface temperature of the detected Suitable areas. There is no possibility of temperature conditions to measure directly inside the refractory lining.

It is therefore the object of the invention to specify a method and an arrangement with which to direct Ways the temperature conditions are detectable in refractory linings.

The solution to the problem can be found in the corresponding claims for procedures and arrangement with continuing versions in the associated Dependent claims.

The core of the process is that between the wall and the lining of the furnace at least one optical fiber arranged and the temperature over a system for distributed, fiber optic backscatter measurement is determined. The measuring principle is known with different variants, for example OTDR or OFDR with Raman, Rayleigh or Brillouin spectroscopy.

The measurement of temperature data and Their electronic evaluation offers a variety of treatment options and control of the furnace processes. The temperature data can be timed and / or spatial recorded, stored, visualized and electronically processed become.

The specific thermal and material technical parameters of the furnace can be included in the evaluation become. Here you can Temperature thresholds, spatial or temporal temperature gradients, extreme values according to the circumstances of the furnace structure are given and taken into account. From a local and / or temporal analysis of the data, reporting events can be derived to the delivery of warning signals and / or the triggering of Intervention operations (for example, automatic shutdown of the Furnace heating). Particularly interesting is the possibility of presenting a spatial and / or temporal temperature profile with a pattern comparison to a reference profile.

The essence of the arrangement is that as a temperature sensor at least one optical fiber in one own layer between wall and refractory lining of the furnace introduced and the at least one optical fiber to the mentioned measuring system is coupled.

One or more optical fibers can be laid in the form of a net in the layer. The network can the shape of a meander or more. Instead of meander can also be the image of one or more spirals from one or more Be laid optical fibers. Several nets can be in a crossed position.

The layer can be used as a web material (in the form of a flexible mat) made of temperature-resistant material be, wherein the temperature-resistant material may consist of mica. The mat can additionally laminated with glass or carbon fibers and reinforced.

It is therefore proposed to use a fiber-optic, distributed temperature measuring system as a monitoring and measuring system for the state of the furnace lining. As optical Rückstreumeß-method, the already mentioned methods can be used; for example, known from the EP 0692705 A1 ,

• – höhere Tiegelstandzeiten und damit Ofenbetriebszeiten durch exakte Bestimmung der zulässigen Betriebszeiten,
• – höhere Sicherheit durch genaue Lokalisation von Hotspots, Prozessvisualisierung und -kontrolle und Warnfunktion durch die Möglichkeit der Datenverarbeitung,
• – schnelle Inbetriebnahme nach Neuauskleidung, da ein aufwendiges Abgleichen des Systems entfällt.

The measuring system consists of various electronic and optoelectronic components and forms a visualization, measuring, evaluation and / or signaling system. The following advantages are associated with the invention:

• - higher crucible life and thus furnace operating times by exact determination of the permissible operating times,
• - Higher security through accurate localization of hotspots, process visualization and control and warning function through the possibility of data processing,
• - Fast commissioning after re-lining, as a complex adjustment of the system is eliminated.

According to the invention, at least one high temperature stable, optical fiber in the form of a Mesh introduced into a mat made of temperature-resistant material. After consumption of the refractory lining - depending on the condition of the build-up layers of the furnace - the mat can be preserved or also cleared out. A fiber (for example made of quartz) coated with polyimide or similar. can be used for temperatures up to 380 to 420 ° C. The length of the optical fiber used depends on the surface area of the mat and thus on the size of the oven and the type of installation. In a 6-ton smelting furnace, a simple meandering installation with a fiber spacing of about 6 cm requires about 80 meters of optical fiber. The far end of the optical fiber may be within the mat.

The beginning of the optical fiber is with a usual optical connector or an optical pigtail. The pigtail or the plug is led out of the oven at a suitable location. About this Pigtail or optical connector is then the connection to Measuring and evaluation unit.

Because of the great length range (up to 4,000 m) commercial Backscatter measuring systems is it quite possible several ovens to monitor with a single evaluation unit by using multiple mats serial over optical connection cables are connected in series. To must then the "end" the optical fiber of a first mat also with an optical Plug or optical pigtail to be connected. Should be a fiber splice lie within the mat, so must the splice protection used be metal-free. This plastic splice protectors come into question which are based on a shrink tubing technology.

To protect a relatively brittle high-temperature optical fiber can the fiber in addition with a secondary Be provided coating (secondary coating). There is one in it significant increase in mechanical load capacity of the optical fiber given, which is advantageous for embedding in the mica mat and on her Handling affects. As a material for coatings are high temperature resistant Fluoropolymers or polyimides known and usable. As a protective serving can additionally or even without special secondary Coating a non-metallic shell (Capton film, Kevlar or Kohlerfasergeflecht) be provided, in which the optical fiber is loosely collected.

Through the proposed installation the optical fiber and a sufficient spatial resolution of the Evaluation unit (optimal 50 cm) can both during operation the creeping abrasion of the lining by the slow increase of the Base temperature as well as local cracks and "metal tongues" by localized Temperature peaks are observed. This is a real online monitoring of the Condition of the refractory lining available. It is understood that used modern electronic and data processing means and procedures can be with which a spatial and / or a temporal temperature profile is determined, stored, retrieved and can be displayed.

The electronic evaluation units can be refined as warning or alarm systems. When heating of the melt after re-lining becomes a base temperature profile recorded as a reference profile and saved. In operation Then every temperature of each data point within the Lining area with the temperature of the data point at the same Compared to the reference profile. Exceeds the temperature difference the data points have a set value, this is called a warning or displayed as an alarm. over the number of so determined "critical" Temperature values make a statement, whether it is a surface abrasion to individual Cracks or "tongue formation" is.

The invention is shown in two figures shown. They show in detail

1 the wall construction of an induction melting furnace and

2 a flexible mat with integrated optical fiber and schematically indicated: the connection to a Rückstreumeß-system.

The invention is intended in l by way of example on an induction melting furnace, but without limitation to this particular type of melting furnace. It is essentially about the basic structure of the layers (A0, A1, A2, W1, W2, W3) between refractory Ausklei tion 30 and wall 40 with integration of at least one optical fiber 10 in a separate layer 20 ,

The coils of an induction melting furnace usually consist of water-cooled copper pipes 60 , They form together with a bobbin balancing mass W 1, the outer wall. Between refractory lining 30 and wall 40 is the mat according to the invention in the one optical fiber 10 is integrated, about capable W3. Preferably, the mat is ( 20 ) constructed as insulating and sliding layer (W3) of mica. Layers A1 and A2 may be formed as a special ceramic interior protection. The layer W2 may consist of further insulating strips or be understood as a component and web material (ceramic fiber fleece) of the mat according to the invention.

In the schematic wall construction of the induction melting furnace shown on the left is the melt 80 , right of Induktoraufliau W 1 with only one drawn in cross-section copper tube 60 , The refractory lining 30 is built with known sintered material in one or more layers (A0, A1, ..).

In one layer (preferably as W3) under the lining 30 (to the hot side of the wall) lies the layer 20 with at least one optical fiber 10 as a temperature sensor.

In 2 is a flexible mat 20 made of temperature-resistant material, which is prepared and inserted before the furnace is re-lined. As an integral part of the mat can - too due to their good slipperiness during thermal expansion - a heat resistant mica variety (eg phlogopite) can be provided. The mat can additionally be reinforced with glass or carbon fibers. The mat covers the wall of the oven or only temperature-critical parts of the wall. In the 2 is hinted that the mat consists of a first 21 and a second half 22 consists of (around a longitudinal edge or a fold 24 ) are folded on each other. In the intermediate layer (or layer joint) 23 is the optical fiber. Before folding the two halves of the mat, the optical fiber can be coated with a suitable temperature-resistant adhesive (silicone) in the layer joint 23 be fixed.

The optical fiber 10 is in the form of a meander network 100 in the mat 20 laid. The main direction of the straight sections of the meander 100 is in the x direction. Transverse to the main direction x, a second optical fiber could be inserted again in a meandering shape, so that their straight line pieces extend in the y-direction. Preferably, the main direction x is placed parallel to the furnace or crucible axis. With spiral laying of one or more optical fibers, the fibers can be laid in spirals left and right handed cover one above the other or partially covering or next to each other.

With reference number 23 is indicated that the optical fiber 10 with a sheath and / or a sheath 12 is provided. The sheath can extend over the entire length of the fiber. The optical fiber 10 is connected to a measuring and evaluation system 14 coupled to the fiber optic backscatter measurement via an optical connection 16.

• – Abpufferung wärmebedingter Ausdehnung der Auskleidung zur Vermeidung von Spulenschäden,
• – zusätzliche elektrische Isolationsschicht zwischen Spule und Schmelze und
• – Erleichterung des Ausbrechen der Auskleidung nach Abnutzung.

The mat according to the invention has, in addition to the measuring function, further advantageous functions, in particular because of its position between the lining and the furnace wall:

• Buffering heat-induced expansion of the lining to avoid coil damage,
• - Additional electrical insulation layer between coil and melt and
• - Facilitate the breaking out of the lining after wear.

10

optical fiber

12

Shell (secondary coating / protective coat)

14

measuring system

16

optical connection

20

sheeting (Mat)

21

first Matt häfte

22

second Matt häfte

23

Schichtfuge

24

fold

x

first Axial direction (main direction)

y

second axially

30

lining

A0, A1, A2

lining layers

40

wall

W1, W2, W3

wall layers

60

water-cooled induction loop

80

molten metal

100

network / Meander

Claims (11)

Method for monitoring the state of preservation of the refractory lining ( 30 ) of furnaces with oven temperature sensor ( 10 ), characterized in that between wall ( 40 ) and lining ( 30 ) of the furnace at least one optical fiber ( 10 ) and the temperature via a system ( 14 ) for distributed, fiber optic backscatter measurement is determined. Arrangement according to claim 1, characterized in that the measuring system ( 14 ) recorded temperature values are processed and stored in an electronic evaluation system. Method according to claim 2, characterized in that the measuring system ( 14 ) are correlated with oven-specific parameters, and that via the correlation an output of warning and / or switching operations can be triggered. A method according to claim 3, characterized in that oven-specific Parameter determined as a reference pattern after each refurnishing of the furnace and saved. Arrangement for monitoring the state of preservation of the refractory lining ( 30 ) of furnaces with oven temperature sensor ( 10 ), characterized in that as a temperature sensor at least one optical fiber ( 10 ) in a layer ( 20 ) between wall ( 40 ) and lining ( 30 ) of the furnace and the at least one optical fiber ( 10 ) to a measuring system ( 14 ) is coupled to the fiber optic backscatter measurement. Arrangement according to claim 5, characterized in that the at least one optical fiber ( 10 ) in the form of a network ( 100 ) in the layer ( 20 ). Arrangement according to claim 6, characterized in that the network as at least one meander ( 100 ) or as at least one spiral of the at least one optical fiber ( 10 ) is formed. Arrangement according to one of claims 5 to 7, characterized in that the optical fiber ( 10 ) with a casing and / or a casing ( 12 ) is provided. Arrangement according to one of claims 5 to 8, characterized in that the layer ( 20 ) is formed as a flexible mat made of temperature-resistant material. Arrangement according to claim 9, characterized in that the material of the mat ( 20 ) consists of lubricious mineral. Arrangement according to one of claims 5 to 10, characterized in that as measuring system ( 14 ) the principle of distributed, fiber optic backscatter measurement is used.